List of top Physics Questions on spherical lenses asked in KCET

A point object is moving at a constant speed of 1 ms-1 along the principal axis of a convex lens of focal length 10cm. The speed of the image is also 1 ms-1 , when the object is at _______ cm from the optic centre of the lens.
The size of the image of an object, which is at infinity, as formed by a convex lens of focal length $30\, cm$ is $2 \, cm .$ If a concave lens of focal length $20 \, cm$ is placed between the convex lens and the image at a distance of $26\, cm$ from the lens, the new size of the image is :
Two thin plano-convex lenses each of focal length $f$ are placed as shown in the figure. The ratio of their effective focal lengths in the three cases is
Which mirror is to be used to obtain a parallel beam of light from a small lamp?